Inert gas eliminator for high altitude oxygen apparatus



Dec. 14, ,1948.

D. S. MARTIN, JR., ETAL INERT GAS ELIMINATOR FOR HIGH ALTITUDE OXYGEN APPARATUS Filed Aug. l0, 1944 "'IIIIIII lA/EWS EDWIN EEGM/LLER @www @muy

Patented Dec. 14, 1948 INERT GAS ELIMINATOR FOR HIGH ALTI- TUDE OXYGEN APPARATUS Don Stanley Martin, Jr., Santa Fe, N. Mex., Norman D. Nachtrieb, Chicago, Ill., and Jarvis Edwin Seegmiller, Salt La to the United States of by the Secretary 0f the Application August 1o, 1944, serial No. 548,882

7' Claims.

This invention relates to automatic nitrogen eliminating mechanism for high altitude oxygen rebreathing apparatus used by flying personnel.

High eliciency in the ultilization of oxygen and the consequent saving in weight are attractive features of the rebreather type oxygen apparatus for aviation use. The gases, still rich in oxygen, which are exhaled from the lungs, are not lost to the atmosphere; instead, they pass through a canister 4containing suitable chemicals and into a exible rubber bag. The chemicals in the canister absorb carbon dioxide from the gas stream and may simultaneously generate oxygen. As oxygen is consumed from the system, it is replaced automatically from a small light-Weight cylinder. Thus, with a satisfactory seal around the facepiece, the rebreather, together With the lungs and air passages of the person, forms a closed gas system from which oxygen can escape only into the blood stream of the body.

A serious disadvantage inherent in the use of rebreather type oxygen apparatus is the danger from inert gas Which enters the system. Such gas consists chiefly of nitrogen and small amounts of the rare gases customarily designated only as nitrogen. The displacement of oxygen by any nitrogen in the closed rebreather system may result in serious or even fatal anoxia at high altitudes. The presence of nitrogen in the gases decreases the safe ceiling for the personnel. Even with the facepiece tted satisfactorily and a tight rebreather system, nitrogen may enter the system from tWo sources. One source is the human body itself, which, in breathing air, dissolves throughout its tissues and fluids an amount of nitrogen of the order of one liter. When a person breathes oxygen, the dissolved gases leave the body by Way of the lungs and when he is using the rebreather apparatus they enter into and remain in the closed system described above. Another source of nitrogen is the commercial breathing oxygen in the auxiliary cylinder which replaces oxygen used up in the rebreather system. A number of analyses have shown that such oxygen cylinders contain approximately 1% of inert gas. Thus the small cylinder used with this type of apparatus, which contains about 200 liters of gas at standard temperature and pressure, would contribute, upon being completely used, approximately 2 liters of nitrogen which would have accumulated in the closed rebreather system.

Prior to this invention it has been the necessary practice for the person using the reb-reather apparatus to manually flush the system out after prescribed intervals, each time replacing the nike City, Utah, assignors America as represented Navy (Cl. 12S-191) using the equipment. In the embodiment shown the venting means is essentially a small pump having valve means and operated by the breathing bag of the rebreathing apparatus during its pulsations. Other objects will become apparent as the description proceeds in connection with the drawings, in which:

Fig. 1 is a sectional view of a rebreathing apparatus incorporating the nitrogen eliminator, and illustrating the ilow of the gases in the system;

v and Fig. 2 is an enlarged sectional view of the nitrogen eliminator shown in Fig. 1, and showing the details of its construction.

'I'he individual supply type oxygen rebreathing apparatus illustrated supplies flying personnel with respirable air that contains the high percentage of oxygen required for high altitude service. The apparatus operates independently of the external atmosphere; the wearer breathes oxygen in a closed circuit, inhaling from a ilexible breathing bag and in turn exhaling through a chemicalpurier back into the breathing bag, from which the unused oxygen is available for rebreathing. The chemical purier, which may, for example, be potassium hydroxide, removes the carbon dioxide from the exhaled air. The oxygen supply that is available for breathing in the bag is continuously replenished in the same amount as that used by the body, in partby automatic admission of oxygen from the high pressure oxygen cylinder, and in part by reaction of the moisture in the exhaled air with the chemical purier which may also include, for example, some sodium peroxide for that purpose. The rebreather system itself will be described i-lrst, and then the operation of the nitrogen eliminator, so that the operation of the combination will be clear.

As shown` in Fig. 1, an apparatus case l houses and supports a breathing bag 2, an admission valve housing 3, and an oxygen reducing valve 4. An oxygen cylinder 6 is attached to the apparatus case by means not shown. A canister is also attached to the apparatus case by means not shown, the canister itself being held in a canister .breathing airpasses Afreely holder 8 which holds both ends, the holder 8 being detachably mounted on the apparatus case I. The canister holder 8 has ttings S and III respectively into which the passageways in the ends of the canister 'I fit. A flexible hose I2 connects .at its two ends'to the fittings 9 and ill), providing a. by-pass around the canister during an inhalation by the person wearing the apparatus.

The fitting Il] has an inhalation check valve I3 which is held lightly againstitsseat -by a-s'pring I4, permitting passage of the air .upwardly through the hose I2 during inhalation, but preventing the downward passage of the air during exhalation, thus requiring the lexhaledfair to pass through the canister 'I whereitfischemicallyfpurified, the chemicals absorbing the exhaled carbon dioxide and also evolving oxygen upon .contact with the moisture in the exhalations.

A flexible breathing tube I5 connects the Yupper fitting 9 to a facepiece IE6, there being a facepiece valve I8 where the breathing .tube connects to -the lfacepiece. Ithe valve .[8 has -an .upper .and The ,normal .positiontof .the valve AI8 lis :the-open position shown Figi, lit being held in this position against its upper seat by 4-a spring I9. When -the lvalve is spring seated .against the upper ,seat .-as vshown .in Fig. .1 .-the vback and -orth through lthe 1valve .housing vrand into the facepiece .from v.the breathing tube, or vice versa. When the -wearer pressesfon the knob ,20 `to force ,the valve against the llower seat, :it simultaneously uncovers the -upper l seat, thus closing 4communication ,between the breathing tube t5 and Vthe :facepieceA5,'butopeningcommunication between ,l

the facepiece .and the .ou-ter atmosphere. The knob 28 is pressed in this-manner;only when/the wearer .-intends .to exhale directly to :the atmos- ,fphere `to eliminate nitrogen from the system as will 4be described.

The tting I0 has open communication with the admission valve housing 3- through afflexible .connecting-.tube 2 I and thefadmission-valve ho using has open communication with :the interior of .the breathing-bag 2 as .shown :in Fig. f1. -The breathing bag a stoekinette-reinforced rubber .storage-reservoir iorthe breathing-airandzoxygen supply. yIt is fof bellows design, permitting .free 'contraction and i exten-sion with minimum resist- .ance when the vwearer :breathes 'finto `and out A'of it through :the aforementioned -.,connecticns. At .thetend .'22 into which the valve vhousing 3 :een tends, the ybreathing .bag :is 1 relatively xed lwith respect tothe apparatus case. lts other -end .2id is .free tomove towards :and: away from the .xed .end `422 v.with thelcontractionand: extension :of the bag. The left= side-fof the f apparatus case .is pro- .vided iwith largeperforations to -vent `ltheinterior ofthe :apparatus A:caseto the atmosphere-and l.prevent lchanges in pressure therein with 'contraction andlextension ofthe breathingbag..

An oxygen vadmission kvalve -is heldagainst its seat vin the admission valve vchamber :2B Iby .means ofasylphon springlr'l. :Oxygen issupplied tothe admission `valvecl'iarnber 2 6 ata pressure of approximately lpounds .perrsquare .in-ch.above the atmospheric v.pressure .from Veither v,of -two sources .to .be described. .An .admission valvelever 28 .is .pivotally V.attached Iat '29 iat `its, ,upper .end to'theapparatus case'and-.at 30 at-itslower `and to-the. moving .end.24 .of the breathing bag. Adjacent .its upperfend the yvalve .lever ,ZBTduring its movement i contacts the movable end .Y oi lthe -.Sylphonspring :21 to unseat .the .valve 25;.andladmit .oxygen to .the `breathing .bag via-.atubef33. .The

.on the oxygen supply. From valve 34 the instant at which the valve 25 is unseated and seated again with relation to the cycles of movement ofthe breathing bag and the admission valve lever 28, is controlled and adjusted by means of an admission valve adjusting screw 3l which is threaded finto the admission valve lever and en gages the Sylphon spring '21 to unseat the admission valve 25.

One source of oxygen is the oxygen cylinder i5 which has azcylinder valve 34 to shut ofi or turn oxygen flows to the reducing valve I which is of the single stage.expanding'bellows type in which the oxygen 1ifiressureis reduced from the cylinder pressure of about 1800 pounds per square inch when the cylinder is full, to a pressure of not more than 'I pounds per square inch above the surrounding atmospheric pressure. As the pressure within the freducing valve builds up to the maximum pressure the expansion vfof the Sylphon 35 forces .the valve 31 .against its seat, as will be under- .stood .by .those skilled Vin the. art.

A gauge .33

measures the-,pressure 4of theoxygen in the cylin- -der B lwhen the .valve -`34 is open.

.From the .reducing valveA '4 the oxygen fflows through .a .passage `4D to the .interior ofthe admission valve chamber '26, and thence, under the control of admission valve 25 .to 'the interior-of the breathing .bag through the tube 33. A check valve connection III, located at lthe top .of the apparatus `case I, isprovided in the event that 'it -is desired .or required 'that the .apparatus be joperated froman auXii-lary or `central oxygen supply 'in place of .the 'individual oxygen cylinder '6 mounted on the side of 'the apparatus case. A passage i3 extends vfrom the check valve connection 4I to the interior o'f the admission valve .chamber 26. When ,the .auxiliaryoxygen supply .is used instead of the cylinder E, this cylinder may be disconnected, and fthe ySylphon 3.5 will rclose the `valve 3.1 against .its seat .to .prevent ,the loss of oxygen through the reducing valve.

When .the ,apparatus .is ,in use, the canister .-'I

.must .be replaced .from time to time. :Means are .provided whereby the system operates as a demand typedurin-g thetime .thatthe spent. canister .reestablishing communicationbetween the fittings .by way. of the. canister.

The .above described Velements .comprise a -re- .breather typeapparatus -fwithcut theinstant invention .applied thereto, and .its operation is as .follows Oxygen -from thefcylinder 6 ypasses to theireducing valveJi wherethe-pressure-is-reduced yto approximately-4, Yand amaximum of 'lipounds per square linch. When the 'breathing lbag 2 is deated dur-ing an inhalation, :movement of `the admission valve Llever #28 causes the .admission valve adjusting escrow-3l to bear against the vSylphon spring .21 and-depress-it, thus unseating the-admissionvalve zfrcm'its seat. Thisallows oxygenftoiow fromthe admission valve chamber 26, through tubeil, andinto-the .breathingbag The flowrof-.oxygenintothe'breathing bagv inlates -it tothe .pointewherethe admission valve lever'28 is raised-and closes-the valve 25 againstiitsseat. Theflow of respirablefair -inrtheapparatus isas follows: 'Upon inhalation @airis drawniromthe anta-.ecc

tting I0, through the flexible connecting tube 2I and into the breathing bag, Which is thereby extended. x

When it becomes necessary to replace the canister I while the apparatus is in use, the apparatus functions as a demand type during the time that the canister is removed. The valves 44 and 45 vare automatically spring pressed to closed position when the canister is removed and inhaled air passes from the breathing bag to the facepiece in the normal manner.

by increased exhalation pressure. Insertion of a new canister unseats valves 44 and 45 and the apparatus functions again as a rebreather.

until the valve I8 is pressed against its lower seat by pressure upon the knob 20. This uncovers the upper seat in the facepiece valve. wearer now exhales, the breath exhausing into the atmosphere through the uncovered upper seat in valve I 8. After exhaling, the knob 20 is released, thus closing the upper seat again and uncovering the lower seat. The wearer then inhales again in the normal manner, holds his breath while depressing knob 20 again, and exdescribed flushing out operations. The eliminator is essentially a small pump operated by the movements of the breathing bag. WithA each operating cycle of the breathing bag meters a small amount o1' gas from the bag out to the surrounding air.

The pumping element is a exible rubber bellows 48, disposed with its axis parallel to the axis of the breathing bag, the bellows being extended and contracted by the breathing bag in its movements. At one end the pumpv breathing the bellows is mounted on and sealed to the outer wall of an inlet valve housing 49. A cap 5I has threaded engagement with the outer wall of the housing 49. At its central porprojects through aligned openings in the iiXed end wall 22 of the breathing bag and the side wall of the apparatus case I. A nut 53 is threaded onto the threaded .portion of the stud 52 and clamps the wall 22 and the wall of the apparatus mounted on thewall of the apparatus case together with the xed end 22 of the breathing bag. A sealing and spacing washer 55 on the stud 52 separates wall 22 and the apparatus case wall and assists in providing an airtight seal where the stud passes through them. A washer 5t under the nut 53 prevents marring of the apparatus case when tightening the nut, and may have a sealing washer similar to 55 between it and the wall of the case.

The inlet valve housing portion 57 which houses a end or" the stud is closed by movable for adjustment or 49 has a hollow stud valve spring 58. The a cap 59 which is rereplacement'of the threaded, and its left side, as appears in Fig, 2, is the valve seat. In its center the bushing has a valve stem guide for the stem 63 of a valve 54. The guide is attached to the bushingr by a strut or spider so that the passage of gases through the bushing is substantially unobstructed. The spring 58 keeps the valve against its seat until it is lifted therefrom by the pressure of the gas when the breathing bag is being contracted. A series of openings 66 in the wall of the cap 5i provide passageways for the gas in the breathing bag to the underside of valve 4. When the valve is unseated the air passing through it exits into the interior of the bellows 4S through one or more openings 6T in the inlet valve housing 49.

The other end of the bellows 48 is attached to and moves with the movable end 24 of the breath-- ing bag, and the valve which discharges the air from the bellows is attached to the movable end of the bellows. A tting I0 has a central passageway therethrough, a radial iiange 7l whichy fits within the last convolution of the bellows, and a cylindrical flange portion 'i2 having both internal and external threads. y The cylindrical porIl tion 'I2 projects through an opening in the movable end 24 of the breathing bag and a nut 'I4 clamps the wall of the bag against the radial iange 1I,` there being sealing washers 'I5 and 'I6 on either vside of the bag and between the nut 14 and flange 7|. A check valve body 'il having a central passageway therethrough, has threaded engagement with the internal threads of the .fitting '10. The valve body has a radial flange portion which provides a valve seat '18. A strut or spider 'I9 extends into the central passageway of the valve body, and at its end it has a radial ange which supports a iiexible valve member valve seat 18'with a slight pressure due to the resilience of'the valve material. This provides a check valve which permits the gases to exhaust under a slight pressure from the interior of the bellows, through the passageway in the `valve body TI and from under the edge of the valve member 8l intotheouter atmosphere, but prevents the from the system enhance entraneefof atmospherm'sairinte-the bellowswhen the pressure-therein; isreduced under the atmcs pheric air; pressure. Thistypel of check valve isfknown as anV Acushnetvalver 'Ilieleitv wall of. the apparatus'- caseof Fig. il, which has the large perforation'sf 23 therein, is removable' by means not' shown'. ViithA thisV wall removed, the check valvebcdy ifi: mayberemcved tov inspect the interior 58l may then be inspected or'replaced'byremoving the cap 59.

In operation` the bellows te: is. contracted and extended together with the breathing bagl in its movements. During ani inhalation byY the wearer the bellows is therefore contracted; and sincevthe pressure of any gas therein will' be increased, the gas will. escape fromv the' bellows byy passing under the edges of the check: valve flf. As the breathing: bag isv extended during an exfhalation by the wearer the bellows1will.similar-ls;y extend and the lower pressure therein will allow the valve H to become unseated and some of the gases from the breathing bag will pass into'- the" interior of the bellows. Thus with every cycle of movements of the breathing bag the' action of the nitrogen eliminator will beto remove a portion: of! the; gases from the breathing bag and exhaust them to the atmosphere. This continuous discharge ol a portion ofthe gases from the breathing bag prevents the accumulation of inert gases in the' re'- breather system and the manuali flushing described above is nok longer necessary.

The venting rate achieved by the eliminator is dependent on the diameter of the'rubber bellows method and also on the depth and rate of breathing, so

that as the wearer breathes faster and` deeper the eliminator vents at ahigher rate. With this particular mechanism the venting rate also depends on the degree of distention of the bellows; For this reason it is possible toadjust theventing ratewithin certain limits by changing the'position of the oxygen admission valve adjusting screw' 3f. Thisadjustmenty determines the minimum degree of inflation of the breathing bag below which oxygen will be admitted from the cylinder B'. When oxygen is admitted before the breathing bag is fully deated, the rubber bellows operates in a more distendedcondition and' pumps out more gas per stroke.

Preferably, the constant of spring 58 is so adjusted that valve Bl will be opened by a differential pressure of approximately 40 millimetersof water between the interior of the breathing bag and the interior of the bellows. will cause nearly the maximum distention of the breathing bag. Thus when the breathing bag is iilled, if the pressure therein becomes toogrea't, the valve 64 will open and gas will be permitted to escape from the system by blowing through the valves il@ and Si. This feature permits excess oxygen, which may be formed" by over pro'- duction of the chemical in the canisteror may result from the adjustment of the admission valve adjusting screw 3l, to be removed automatically without discomfort for the per"- son using the rebreathing apparatus.

The invention may be embodied other specific forms Without departing from the spirit or essential characteristics thereof. The present embodiment is, therefore, to be considered in all respects as illustrative andY noti restrictive, the scope of the invention' being indicated by the appended claims rather than by tl`1e1 foregoing description, and all changes whichi come within the This pressure f of the bellows.. The-spring i meaningandrange of equivalencyct the claims are; therei'ore, intended.v toibe embraced therein.

l. In an oxygen.apparatus-'comprising a ilexibl'e breathing bag; which. expands and contractswith the: entranceL andi exit of gases therefrom; ai-face mask; means forming passageways by which the wearer breathes from and into said breathing bag; meansby which oxygenk is supplied to make up for the loss of oxygen in'` the apparatus; and automatici means operated by said breathing bag in4 itsf movements and operable to discharge a portion ofthe gases from the almiratustov prevent an accumulation of inert gases therein, a pump 5 having inletl valve means communicating With the breathing bag and outlet valve means exhausting to the atmosphere 2; In an oxygen apparatus'comprising a flexible breathing bag which expands and contracts with the entranceand exit of n gases therefrom; a face mask-i means: forming passageways by which the wearer breathes from and into said breathing bag; means by which oxygen issupplied to make up4 for the loss of oxygen in the apparatus; and automatic means operated by said breathing bag in` its movements and operable to discharge a portion of the gases Jfrom the apparatus toy prevent a-nf accumulation ofI inert gases therein, a flexible bellows typepump having inlet valve means communicating with the breathing bag andoutlet-valve mea-ns exhausting to the atmosphere. f

3l. In an oxygen apparatus comprising a flexible breathing bag which expands and contracts with the entrance and exit of gases therefrom; a face mask; means forming passageways by which the wearer breathesfifrom and into said breathing bag.; means byl whichoxygen is supplied to make up for the loss of oxygen ih the apparatus; and automatic means operated by said breathing bag in'` its movements and operable to discharge a portion. of the gases from the apparatus to pre-v vent an accumulation'- of inert gases therein', a pumpr having inletv valve means communicating with. the breathing bag and outlet valve means exhausting to the atmosphere, beth of said valve means being of the check valve type operable by differential gas pressures.

4i. Inu an oxygen apparatus comprising a ilexible breathing bag which expands and contracts with the entrance and exit of gases therefrom; a face mask; means forming passageways by which the wearer breathes from and' intoy said breathing bag; means by which oxygen is supplied to make up for the loss of oxygen in the apparatus; and automatic means operated by said breathing bag in its movements and operablekto discharge a portion of the gases from the apparatus to preven-t an accumulation of inert gases therein, a bellows within said breathingr bag, the bellows contracting and extending with said `breathing bag in its movements; a valve inlet means; from said breathing bag tofsaid bellows; and valve outletz means from said bellows to thel atmosphere.

5; An inert gas eliminator for an oxygen apparatus wherein the wearer exhales into and inhale's from' a breath-ingV bag, comprising a bellows adapted to fit intoithebreathing bag and operable to beV extended and contracted by the breathing bag in its movements;y first valve means at one end of said bellows operable to admit gas from the breathing bag to said bellows; and second. valve means at the` other end atmosphere.

y of said bellows operable to exhaust gas from said bellows to the 6. The device described in claim 5 wherein said irst and second valve means are check valves which open by diierential pressure but prevent the passage of gas therethrough into the breathing bag.

7. The device in claim 5 wherein said rst and second valve means are check valves which open by differential pressure, the opening pressure of said first valve being adjustable and said second Valve being removable whereby said first valve 10 may be reached for adjustment.

DON STANLEY MARTIN, JR. NORMAN D. NACHTRIEB. J. EDWIN SEEGMILLER.

REFERENCES CITED UNITED STATES PATENTS Number Name Date Bamberger et a1. July 25, 1905 Paul et a1. May 8, 1917 Drager II Oct. 30, 1923 Drager I Dec. 8, 1925 Von I-Io Oct. 8, 1f940 Weltz Dec. 30, 1941 Wildhack Jan. 13, 1942 

